Hello and Water Pump Question

[timandsam]

Hi All! About 6 months ago my wife purchased a super clean alpine white 2010 X5 3.0i. This is our first BMW and we both really enjoy the car! I have already done a trans fluid/pan change, front and rear diff fluid, transfer case fluid, drive belt, belt tensioner, and the engine partitions. It currently has 99K on it.

Now I am seeming to have an issue I am hoping you guys can give some advise on...

On Sunday night, my wife started it up (the engine was completely cold) and there was a LOUD high pitched whining noise coming from under the hood. I had her rev the engine but it was apparent that the noise did not fluctuate with engine speed. I had her shut the car off and restart it. The noise want away and we drove home without issue (about an hour and a half).

On Monday, I took the X5 to work. At lunch, I sat in the car and let it idle for about an hour while I ate. When I shut it off, i got out and noticed a coolant smell. I looked under and saw no signs of leaking and went inside thinking i would check it out later. When I came back outside about a half hour later there was coolant all over the ground. Upon inspection, it appears as though the leak is coming from the bottom of the expansion tank.

We got the car towed home where it currently sits. A high temp light never came on, but the low coolant level warning did come on when we drove it on to the tow truck.

So, my question to you guys is, are the noise and the blown out expansion tank related? Are these both symptoms of a bad water pump?

I would hate to just replace the surge tank just to have the car overheat 5 miles up the road.

What do you guys think?

Thanks in advance!!!
-Tim